Optimizing 6-benzylaminopurine for micropropagation: A cyclodextrin monomers and polymers approach

In the face of escalating climate change challenges, there is an imperative to enhance crop resilience and productivity. The plant growth regulator 6-benzylaminopurine (BA[P]) shows considerable potential in agriculture, yet its practical use is hampered by low water solubility and susceptibility to light and heat instability. This study addresses these limitations and addresses the transformative potential of complexing 6-BAP with cyclodextrins (CDs) or CD-based nanosponges (CD-NS). Calculations of inclusion constants of various CDs gave the opportunity to synthetize the best CD-NSs for BAP complexation, being β-CD the best one (K_F = 289.50 ± 23.16 M^-1). A general enhancing effect observed for CD-based polymers than monomeric ones: The complexation efficiency was determined and compared (67 % monomers vs average 89 % for the polymers), as well as their improved water solubility, controlled release (βNS-CDI > β-CD > βNS-CA), and increased bioavailability in vitro. Furthermore, CDs and CD-NS offer effective protection against thermal degradation, potentially extending the shelf life of 6-BAP formulations, which is shown by an enlarged effect in shoots of Prunus salicina LIndl, with applications in agriculture. Thus, shoots cultured in vitro in culture media supplemented with these complexes showed an improvement in the shoot production rate along with an increase in the endogenous BAP and riboside BAP. With the main objective to demonstrate the increase of capacity of BAP-based complexes, this research lays the foundation of the eco-friendly use of dextrin-based polymers for micropropagation improvement.